High speed small deflection interlace mirror

ABSTRACT

A small deflection scanning mirror having a sufficiently high resonant frequency so as to be suitable for high speed interlace operation. The mirror structure includes a balanced pair of mirror surfaced plates arranged parallel to each other on opposite sides of a mounting plate and with a honeycomb core therebetween formed of an array of stacks of linear motion transducers or motors. Each stack may have selected numbers of the transducers connected either in series or in parallel or in series-parallel combinations. The stacks in the array are arranged to develop a deflection profile over the plates chosen for minimum bending of the surfaces while providing the required total deflection in response to drive waveforms of proper polarities. Because the drive is applied in a distributed manner, resonant frequency considerations apply mainly to the crystal structure of the stacks and the amount of distributed mass loading from the mirror plates, and the mirror size or total mass is no longer a significant resonant consideration.

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Laakm June 26, 1973 HIGH SPEED SMALL DEFLECTION Primary Examiner-JamesW. Lawrence INTERLACE MIRROR Assistant Examiner-D. C. Nelrns [75]Inventor: Peter Laakmann, Los Angeles, Calif. :32:3 MacAnlster andWalter [73] Assignee: Hughes Aircraft Company, Culver 57 ABSTRACT FilediJulie 1971 A small deflection scanning mirro r having a sufficiently 2App] 155 55 high resonant frequency so as to be suitable for high speedinterlace operation. The mirror structure includes a balanced pair ofmirror surfaced plates ar- [52] US. Cl 250/235, l78/7.6, 350/6, rangedparallel to each other on Opposite Sides of a 359/295 mounting plate andwith a honeycomb core therebe 51 Int. Cl. n01; 5/16 tween formed of anarmy of Stacks of linear motion [58] Field of Search 250/234, 235, 236;transducers or motom Each Stack may have Selected 350/6 285; 178/7-6numbers of the transducers connected either in series or in parallel orin series-parallel combinations. The

[56] 1 References Cited stacks in the array are arranged to develop adeflection UNITED STATES PATENTS profile over the plates chosen forminimum bending of 3, O71,036 1/1963 McKnight 250/235 the Surfaces WhileProviding the required total deflec- 3,080,484 3/1963 Hulett 250/235tion in response to drive waveforms of proper polari- 3,166,683 1/1965Gootherts 350/6 ties. Because the drive is applied in a distributed man-3,532,408 Dostal ner resonant frequency considerations mainly to3,020,414 2/1962 McKnight 250/235 the crystal structure of the stacksand the amount of 3,386,786 6/1968 Kaisler 250/235 distributed massloading from the mirror p and the mirror size or total mass is no longera significant resonant consideration.

11 Claims, 9 Drawing Figures 0 I020 IOlo I000 I03 I050 I040 L g 74 g a 2a i E 2 e; a 25 :F H 1 J "l 89 04 lO2b IOOb 3742234 2 0R mt 250/235 1 aPATENTEDJUHZB I973 3 742.234

Apparent detector motion on ground Interloce l4 Ngrmul Position PositionDetectors Signal Process ing Fig.2.

Peter Loukmonn,

INVENTOR.

wwazya a ATTORNEY.

PATENTED JUN 26 I975 SHEET 2 BF 4 T 4&

FATENIEuJms am SHEEHLBF4 p Fig. 8.

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HIGH SPEED SMALL DEFLECTION INTERLACE MIRROR BACKGROUND OF THEINVENTION 1. Field of the Invention This invention relates to scanningmirrors and particularly to a high speed small deflection mirrorsuitable j for use in mechanical interlace operations such as forscanning detector arrays.

2. Description of the Prior Art In systems requiring high speed opticalscanning such as in infrared systems where rapid mechanical interlacescanning of a detector array is required, it has been found to bedifficult to move large mechanical mirror structures through very smallangles at very high rates such as in kilocycle range. For a selectedinterlace such as a two-to-one or four-to-one interlace, the mirrorwhich receives energy signals from the scene being viewed is required tomove through relatively small angles at a very high rate. One of thedifficulties encountered is that the resonant frequency of the drivermirror must be much higher than the drive frequency in order to avoiddynamic optical abberrations. A second consideration is that theinterlace device or mirror must not exert forces on the'supports, asotherwise the resonant frequency of the supports must be also very high.For some high frequency scanning operations, the required resonantfrequency may be as high as kilocycles and above, which resonantfrequencies are not generally found in normal scanning structures.

SUMMARY OF THE INVENTION Briefly, a high speed small deflectioninterlace type mirror, in accordance with the principles of theinvention, is provided with the drive applied in a distributed, balancedand graduated manner to develop a relatively high resonant frequencystructure while exerting substantially no dynamic forces onto thesupport. The structure, which has a balanced configuration, includes twoparallel mirror plates that form the faces of a honeycomb or sandwichtype structure with a central mounting plate positioned at a neutralaxis between and parallel to the two parallel mirror plates. The core ofthe structure is simulated by the use of an array of linear motiontransducers or drive motors such as electro or magnetostrictivetransducers excited by properly selected high voltage square waves. Thearray includes stacks of the transducers symmetrically arranged onopposite sides of the mounting plate to provide a balanced structure.The deflection profile over the mirror I may be shaped by variableexcitation voltages or by variable numbers of energizable transducers ineach of the stacks. Thus, bending forces in the mirror can besubstantially eliminated. Also, resonant frequency considerations aredetermined mainly by the mass of the crystal material of the linearmotion transducers and the amount of distributed mass loading from themirror attributable to that individual stack. Thus, the size of themirror is no longer a consideration as the scanning drive movement isapplied in a distributed manner. The principles of the invention areequally applicable to angular deflection of curved surfaces as well asflat parallel plates.

It is therefore an object of this invention to provid a high speeddeflection mirror;

It is a further object of this invention to provide a high frequencydriver mirror having a very high resonant frequency, substantiallyindependent of the gross mass of the mirror or of its mounting.

It is a still further object of this invention to provide a high speedsmall deflection interlace mirror that is balanced so as to not applyoscillating forces onto the support.

It is another object of this invention to provide a high speed smalldeflection interlace mirror for use with infrared detectors so as toreduce the number of required detectors or increase the angular coveragefor a given number of detectors.

BRIEF DESCRIPTION OF THE DRAWINGS The novel features of this inventionas well as the invention itself, both as to method of organization andmethod of operation, will best be understood from the accompanyingdescription taken in connection with the accompanying drawings, in whichlike reference characters refer to like parts, and in which:

FIG. 1 is a schematic perspective diagram of an aircraft and a detectorarray utilized therein for illustrating the system for terrain scanningwith a selected interlace, in which the high speed deflection mirror ofthe invention may be utilized;

FIG. 2 is a schematic diagram showing the detector array and the highspeed mirror in accordance with the invention for further explaining itsinterlace operation;

FIG. 3 shows another detector array in accordance with the invention forexplaining a four-to-one interlace operation;

FIG. 4 is a schematic plan view of the high speed mirror deflectionsystem in accordance with the invention;

FIG. 5 is a sectional view taken at lines 5-5 of FIG. 4 showing thestacks of electro-strictive transducers for further explaining the highspeed deflection mirror in accordance with the invention;

FIG. 6 is a schematic side view of a stack of electrostrictivetransducers connected in parallel manner;

FIG. 7 is a schematic side view of a track of electrostrictivetransducers connected in a combined parallel and series manner;

FIG. 8 is a schematic diagram of voltage as a function of timeillustrating waveforms that may be utilized for driving the transducerstacks utilized in the system of FIG. 4, and

FIG. 9 is a schematic diagram showing the overall non-bending motion ofthe schematic mirror of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIG. 1, ahigh frequency deflectiol: mirror 10 in accordance with the principlesof the invention is shown schematically to explain its relation to adetector array 12 and a reflective mirror structure 28, which mirror,array and mirror structure may be mounted near the bottom of'an aircraft16. The detector array 12 may include infrared detectors in theillustrated example in accordance with the invention. Portions of aground area 18 after reflection from the reflective mirror structure 28and the oscillating interlace mirror 10 is seen by the detector array12. Because of the optics of the system, the ground area from whichenergy is received by the detector array is effectively equal to thearea indication 14 which includes for the four detectors, respectiveprojected fields of view 13, I5, 17 and I9 representing the normalposition of the mirror 10. Dotted fields of view 21, 23, 25 and 27represent the interlace position of the mirror 10. Arrow paths such as29 indicate the apparent motion of each detector on the ground orsurface being detected. It is to be noted that the frequency ofinterlace must be sufficiently high to sample each position of interlaceat least once during the time it takes a point source to traverse thedetector field of view, which is a function of the aircraft forwardvelocity. The forward motion of the aircraft 16 or a suitable forwardscan system (not shown) provides the second dimension of movement to theoverall scanning system. Energy rays between the reflective mirror 28and the projected fields of view are shown to further indicate therelative relationship of the normal and interlace positions.

Referring now also to FIG. 2, the detector array 12 is shown withcomposite leads 20 and 22 which include pairs of leads from eachdetector that pass to a signal processing system 23. The mirror whichhas surfaces that oscillate relative to a deflection plane 75 orapproximately around an axis in a plane 24, is mounted on a mountingstructure 25 to receive light passed through an optical structure 30from the ground 18 and reflected from the parabollic reflector structure28, to scan or oscillate so that the radiation from the normal and theinterlace positions is passed to the detectors. Referring also to FIG.1, when the mirror 10 is in a first or normal position, the projectedfield of view of each detector is shown by blocks 13, 15, 17 and 19 andthe data is detected by the detectors 38, 39, 40 and 41 and applied tothe signal processing unit 23. During the sec-.

ond period or mirror position, the detectors see or are responsive tothe adjacent field of view indicated by 21, 23, 25 and 27 and this datais applied to the signal processing unit 23. The detectors 38, 39, 40and 41 are spaced a distance I apart for the two-to-one interlace sothat when the mirror 10 is in the second position, the data previouslydetected in the fields of view 13, 15, 17 and 19 is projected on a blankportion of the array 12 so as to not be detected. For convenience ofillustration in FIG. 2, the four beams of energy shown such as 31 fordetector number 1 or detector 38 is for only the normal position of themirror 10, and a position with a slightly different angle (not shown)would be received when the mirror 10 is in the interlace position.Although the energy beams are shown passing through the opticalstructure 30 to the reflector structure 38, it is to be understood thatdirection changes as well as focusing may be provided by the opticalunit 30, as is well known in the art. The frequency of the oscillationor scanning of the mirror 10 must be sufficiently high to sample eachinterlace position at least once during the time it takes for a pointsource on the ground to trai verse the forward moving detector field ofview such as 13:The use of interlace scanning reduces the number ofrequired detectors or improves the angular coverage that may be providedwith a given number of detectors. It is to be noted that the principlesof the invention are equally applicable to other interlace ratios suchas 4:1 or 8:1 or any other desired ratioI Referring now to FIG. 3 aswell as to FIG. 2, a detector array 46 is shown for illustrating afour-to-one interlace including detector elements 48 through 51 eachhaving a width 1 and being separated by a width 31. The detected signalfrom the detectors 48 through 51 is passed through composite leads 62and 64 to the signal processing unit 23 (FIG. 2). The field of eachdetector moves to four positions on the ground in response to fourpositions of the mirror 10. Thus as the detector 48 receives energy fromthe field of view in four sequential positions, the energy from thepatch of ground in the first field of view position moves sequentiallyalong the array from positions 1 to positions 2, 3 and 4, thenrestarting the sequence, for example. The detector 48 then receivesenergy from four different and adjacent positions on the ground as themirror 10 assumes four positions. The rate of sampling which correspondsto the rate of deflection mirror position change must be such as tosample each ground space at least once during the period a point sourceof predetermined size travels through the detector field of view in thedirection of aircraft travel. A four-to-one interlace allows use of anarray with one fourth of the number of detectors for the same groundwidth to be scanned, or allows scanning of a greater angle for an arraywith the same number of detectors.

Referring now to FIGS. 4 and 5, the high speed interlace mirror 10 isshown in greater detail in accordance with the invention, having amounting plate 67 mounted in the structure 25 at four points and havingexternal plates 69 and with respective mirror faces 66 and 68. Theplates 69 and 70 may be of any suitable rigid material such asberrillium or steel or any rigid metallic or nonmetallic material orcombination of material polished after assembly, having a circularconfiguration and being of equal size and configuration. The mountingplate 67 may be of any suitable rigid structure such as berrillium orsteel or any rigid metallic or nonmetallic material or combination ofmaterial and may have holes therein for electrical conductors, ifdesired. The plates 69 and 70 as well as the mounting plate 67 may be ofany desired shape such as circular, elipsoidal, square, rectangular orany other symmetrical shape, in accordance with the invention. Also, themounting structure may contact the plate 67 at any desired number ofpoints such as three or continuously in some arrangements in accordancewith the invention. To assure a balanced structure, both plates 69 and70 have similar surface polish characteristics, although only thesurface 66 is utilized in the system of FIGS. 1 and 2. The mountingplate 67 is positioned between the plates 69 and 70 so that a balancedsystem is provided around a structure neutral plane 24 formed by theplate 67. Each plate 69 and 70 may be considered to have a respectiveneutral axis 77 and 79 through a mirror neutral plane 75, which are zeromotion axes around which the respective plate rotates. The plane 24 maybe generally considered the neutral plane of the structure and the planemay be considered the neutral plane of mirror movement from the plane24. The surface 66 may be divided into a left-half portion 72 and arighthalf portion 74. A power source 76 and a synchronizer source 78 arecoupled to a pulse forming circuit 79 which provides driving pulses tocomposite leads 80 and 81 which pass to the left-half portion 72 and composite leads 82 and 83 which pass to the right-half portion 74.Positioned between the two plates 69 and 70 are a left-array 88 and aright-array 89 of stacks of transducers, which arrays are symmetricalrelative to the mirror neutral plane 75.

Referring now also to FIGS. 6 and 7, each array forms a honeycombsandwich of rows 11-1 to R-6 on both sides of the axis 24, of stackssuch as stacks to 111, each stack including electro or magnetostrictivetransducers such as 124 to 128 of the stack 100 and such as 115 to 124of the stack 105. The stacks 100 to 111 in FIG. 4 indicate partialstacks 100a to 111a in the top half of the array and partial stacks to 111b in the bottom half of the array as shown in FIG. 5. The electro ormagnetostrictive transducers may be of any suitable material such as,for example, barium titanate, strontium titanate or lead zircanate forelectrostrictive transducers or such as, for example, nickel or nickelalloy (with the current applied to suitable coils to generate a magneticfield) for the magnetostrictive transducers. The transducers may beresponsive to the current or field direction and magnitude to eitherexpand or contract in linear dimension along the length of the stackbetween the two plates 69 and 70. The requirement for the transducers isthus a material that is responsive to either a voltage differential or acurrent differential to change dimensions. a

In one arrangement, in accordance with the invention, the electro ormagnetostrictive stacks of transducers are connected in parallel such asin the stack 100 so that the voltage applied to leads 140 and 142 isapplied between the entire stack of elements which may be 30, forexample. The transducers such as 128 and 129 are separated by a suitableinsulator such as a ceramic material with conductive plates 146 and 148on each side thereof in contact with the transducer material andconnected to suitable conductor strips or leads. The stacks are suitablyattached to the plates 69 and 70 such as by bonding with a suitableadhesive. Also, the transducers, insulators and conductive plates may bebonded together with any suitable adhesive. In another stack arrangementin accordance with the invention, the transducers may be connected inseries to divide the voltage or partially connected in series andpartially in parallel as shown by the stack 105. Transducers 115, 116,117, 122, 123 and 124 are shown connected in series in the stack 105 andtransducers 118, 119, 120 and 121 are shown connected in parallel in thestack 105. When constant level voltages are applied to all stacks, aparallel connection provides a fixed large voltage to each transducerwhile the series connection provides a fraction of the voltage to eachtransducer, thus providing a control of the amount of linear movement.Leads 150 and 152 apply a signal to the transducers of the stack 105. Itis to be noted that for a balanced system, the stacks and transducerconfiguration is similar rela tive to the mirror neutral plane 75 forthe array halves 88 and 89.

Before further explaining the illustrative stack configuration, some ofthe factors that may be utilized in accordance with this invention topnovide the controlled deflection of the plates 69 and 70 will befurther explained. The stacks may be arranged relative to the mirrorplane 75 so that deflection positions 182 and 184 of FIG. 9 are providedwhen the proper voltages are applied to each stack. Although in theillustrated arrangement, constant voltage amplitudes are applied to eachstack (inverted voltages to the two halves 88 and 89 of the stack), itis to be understood that the invention is not limited to thisarrangement, and different voltages may be applied to different stacksor groups of stacks within the scope of this invention. The transducermotion in a direction orthogonal to the surfaces of the plates 69 and 70is proportional to the voltage per centimeter (in the directionorthogonal to the surfaces of the plates 69 and 70) times the length inthe same direction of the crystal in centimeters. Thus, de-

flection is proportional to V the total effective voltage along a stack.The total voltage V, for parallel connected crystals is equal to u Vwhere "p is the number of crystals in parallel in the stack and V B isthe applied voltage. In order to prevent the plates from flexing andachieve true angular deflection, the total voltage V is madeproportional to the radius R with six rows R4. to R-6 being selected foran illustrative example in the arrangement of FIG. 4. Assuming that therows are at one inch intervals from the axis 24, the stacks of each ofrows R1 to R-6 have the same stack configuration in each row. The rowsR-l to R-6 are symmetrical on both sides of the plane in the type ofsystem where the axis of rotation is in the center of the plates. Alsoin the example, 200 volts per crystal is the selected maximum incrementwith 30 crystals selected per total stack such as including bothportions 100:: and 10%. Calculations may be based on the entire stack orthe upper and lower portion of the stack in accordance with theinvention, giving consideration to the requirement of symmetry above andbelow the neutral plane 24. For the row R-6, all stacks thus require a Vof 6,000 so all 30 transducers are connected in parallel as indicated inFIG. 6. In row R-S, which requires a V of 5,000 volts, 24 transducersare connected in parallel, two .transducers are connected in series andfive are left unconnected, for example. In row R-4, which requires a Vof 4,000 volts in each stack, 20 transducers are energized and 10 areunconnected, for example. In each stack of row R-3 for a V, of 3,000volts, l4 transducers are connected in parallel, two transducers areconnected in series and 15 transducers are unconnected, and in eachstack of row R-2, l0 transducers are connected in parallel and 20 areunconnected. For row R-l each stack may be connected as shown in FIG. 7to provide a V, of 1,000 volts so that four transducers are connected inparallel, 26 transducers are connected in series (or two in series and24 unconnected). It is to be noted that any suitable configuration ofparallel and series transducers are unconnected transducers for thestack arrangements is within the scope of the invention.

The stacks as shown in FIG. 4, are offset horizontally between adjacentrows so that each stack controls substantially the same area of plate.The number and diameter of the stacks is selected or adjusted for aproper resonant structural frequency. The crystal resonant frequencycontrols the limit of the upper range of resonant frequency. The spacingof the stacks is selected for a desired resonant frequency byconsidering the distributed mass of the plate or plates allocatable toeach stack plus the transducer distributed mass relative to thestructure neutral plane 24. Dotted circles, 132, 133 and 134, of FIG. 4show the plate area allocated to each linear motion transducer stackwhich is utilized to determine the spacing and transducer diameter forspecified resonant frequency requirements, the resonant frequency beinga function of the distributed mass of the transducer stack and theselectable distributed mass of the plates. Also, it is to be understoodthat in some arrangements in accordance with the invention,approximations'may be required in both the connecting of the stacks andthe positioning of the stacks to provide a desired plate motion withoutincreasing the mass of any one stack unit appreciably.

It is to be noted that the mirror surface or surfaces being driven bythe driving arrays 88 and 89 are not limited to a flat surface and, forexample, doubly curved surfaces 172 and 174 shown dotted in FIG. 5, andwhich may be spherical or aspherical, may be provided (with properselection of the stacks of electrostrictive transducers and the drivingvoltages) within the principles of the invention, such as for use in acassegrain antenna or similar type system.

Referring now to FIG. 8 as well as to FIGS. 4 and 5, voltage pulses ofwaveforms 180 and 182 may be utilized for the two-to-one interlace(illustrated in FIG. 2) with the pulses of the waveform 180 beingapplied to the leads such as 82 and 83 and in turn to leads such as 140,142 and 150 and 152 of the right hand array 89, and with the pulses ofthe waveform 182 being applied to the leads such as 80 and 81 and toindividual leads such as 140, 142, 150 and 152 of each stack in the lefthand array 88. In the arrangement shown, one of the leads for each ofthe stacks may be grounded and the pulses of the waveforms 180 and 182may be applied to the other lead of each stack. For the four-to-oneinterlace as explained relative to FIG. 3, pulses of waveforms I84 and186 may be respectively applied to the right hand array 88 and to theleft hand array 89. Thus, in the illustrated arrangement, the voltagepulses are applied to provide symmetry to the mirror, for instance, andsimilar stacks are used on both sides of the axis 24 with inverteddriving pulses applied to different halves of the array. Dotted lines190 and 191 illustrate that in some arrangements in accordance with theinvention, a space may be provided for an electronic box to include thepulse forming and other required circuits.

It is to be understood that the principles in accordance with theinvention include variations such as use of stacks of differentmaterials, applying different voltages to different stacks, combinationsof different materials and series and parallel connections, any suitablespacing to provide the desired configurations with a minimum of bendingand the use of stacks of different types of material all connected in asimilar manner such as series or in parallel or all connected in anydesired combination of series and parallel.

Referring now also to FIG. 9, which shows two scan positions of thesurfaces 66 and 68 for a two-to-one interlace, position 182 representsthe positions of the surfaces as a result of the high or positivevoltage being applied to the array 89 and the low or negative voltagesbeing applied to the array 88, and a dotted position 184 represents theposition of the surfaces as a result of high voltages being applied tothe array 88 and relatively low or negative voltages being applied tothe array 89. Because each stack has a mass that is a function ofsubstantially only the crystal material and a predetermined area of theplates, the resonant frequency of the mirror structure is relativelyhigh. Also, because the transducer or motor operates in a balancedmanner, a relatively small amount of reaction forces are applied to themounting structure 25. Although the illustrated system has the neutralplane 75 in the center of the plate, it is to be understood that theprinciples of the invention are applicable to a structure having theneutral axis on the edge or any desired position between the two edges.

Thus there has been described a compact interlace mirror and driver thatproduces essentially a square wave interlace with frequencies as high asseveral kilocycles or higher for relatively small deflection angles suchas less than 50 microradians, for example. Be-

cause of the high resonant frequency of the mirror and becausesubstantially no reaction forces are applied to the mounting structure25 so as to require the support to have a high resonant frequency, theconcept can be applied to large mirrors with substantially no penalty inspeed of operation and is applicable to high interlace ratios such asfour-to-one or higher. The resonant fre quency is a function of the massend loading area of each piezoelectric stack and the crystal mass andspring constant, rather than of the mass and parameters of the entirestructure. Thus, the scan mirror of the invention moves to differentpositions without causing reactions against the support structure and atfrequencies exceeding the flexure resonant frequencies of the scanmirror and of the support structure. Also, in accordance with theprinciples of the invention, the pulse forming circuit may be positionedinside the mirror around its neutral axis to provide a highly compactunit. Although the system is not to be limited to any particular voltagelevel, it has been determined that typical systems using crystals wouldoperate with voltage levels between several hundred and several thousandvolts. The transducers may be any suitable material such as anelectrostrictive material with signals applied directly thereto in aseries or parallel manner as with coils that are connected in series orin parallel or are capable of providing selected magnetic fields. Thesystem makes possible the use of interlaced arrays for higher resolutionpictures with the consequent reduction of detectors for the same angularcoverage, to 50 percent in the claimed two-to-one interlace and to 25percent for a four-to-one interlace. The principles of providing anoscillating surface are not to be limited to mirror scanning but areapplicable to other uses where a high frequency oscillation is required.

What is claimed is:

1. A scanner comprising first and second plates having a symmetricalconfiguration relative to each other and a deflection plane orthogonaland through the surfaces of said plates,

mounting means positioned in a plane between and parallel to said firstand second plates,

an array having first and second portions and positioned between saidfirst and second plates and including a plurality of stacks of linearmotion transducers arranged substantially symmetrical relative to saiddeflection plane, each stack having said first and second portions onopposite sides of said mounting mirror,

and a source of pulses coupled to said linear motion transducers so thateach stack controls movement of an area of each of said plates so thatsaid first and second plates each move around a rotation axis includedin said deflection plane.

2. An oscillating mirror system comprising first and second circularplates of a rigid material positioned with a selected spacetherebetween, said plates divided into first and second semicircularportions on opposite sides of a neutral plane perpendicular to thesurfaces of said plates,

a mounting plate positioned between and parallel to said circular platessubstantially half way therebetween,

first and second groups of stacks of transducer elements positionedbetween said first and second plates at said first and second portionsrespectively, said stacks positioned in each group in a preselectedpattern symmetrical relative to said neutral plane, each stack havingfirst and second portions positioned on opposite sides of said mountingplate,

a source of pulses coupled to the stacks of said first and second groupsto apply a first pulse pattern to said first group and a pulse patterninverted with respect to said first pulse pattern to said second group,whereby said first and second plates are deflected by rotation around anaxis through said neutral plane so that sequentially the first end has asubstantially greater spacing between said plates than the second endand said second end has a substantially greater spacing between saidplates than the first end.

3. The combination of claim 2 whereby transducer elements energizable bysaid source of pulses and substantially adjacent to first and secondends are connected in parallel and other transducer elements energizableby said pulses are connected with selected combinations of parallel andseries connected transducer elements therebetween.

4. The combination of claim 3 whereby said transducer elements areelectrostrictive elements and the voltage pulse patterns are symmetricalaround a reference voltage with each of said transducers coupled to saidreference voltage.

5. The combination of claim 3 whereby said transducer elements aremagnetostrictive elements.

6. A high speed interlace mirror system for receiving energy fromsources on a surface comprising first and second plates of a symmetricalconfiguration with respect to each other positioned at a predetermineddistance apart with at least the surface of said first plate beingpolished to reflect energy received from said source, said first andsecond plates having a neutral plane through the center thereof andorthogonal to the surfaces thereof,

means for mounting said first and second plates positioned in a mountingplane between and parallel to said first and second plates,

a plurality of detectors arranged to receive reflected energy from thesurface of said first plate,

first and second groups of stacks of electrostrictive transducerspositioned in a selected pattern respectively on opposite sides of saidneutral plane between said first and second plates, said stacks havingtransducers therein selectively connected in parallel and in series withstacks arranged in a predetermined pattern symmetrical around saidneutral plane, each stack having first and second portions respectivelypositioned on opposite sides of said mounting plane,

a source of voltage pulses coupled to the stacks of said first andsecond arrays, said source of pulses applying a first pulse pattern tosaid first array and an inverted pulse pattern to said second array,said first pulse pattern and said inverted pulse pattern each having aplurality of voltage levels to define step positions for interlacingenergy from different positions of said surface.

7. A high speed scan mirror mounted on a support structure comprisingfirst and second plates positioned parallel to each other with thesurface of at least one forming a mirror, said plates having a planetherethrough substantially perpendicular to the surfaces thereof,

a mounting plate structure positioned parallel to and between said firstand second plates and attached to said support structure,

a plurality of electrically controlled first and second drive motormeans respectively positioned between said first plate and a selectedposition of said mounting plate structure and said second plate and saidselected position of said mounting plate structure adjacent to aselected area of both plates, so that each corresponding first andsecond motor means applies equal and opposite reactions to said mountingplate structure to cancel the reactions so that relatively smallreactions are applied to said support structure.

8. A controllable structure comprising first and second plates of arigid material positioned substantially parallel to each other,

a mounting plate positioned parallel to and between said first andsecond plates,

an array formed of a plurality of stacks of transducers positionedbetween said first and second plates with each stack having first andsecond longitudinal sections having controllable lengths, and eachcontacting a selected position of said mounting plate each forcontrolling the distance between said first and second plates and saidmounting plate of a selected area of said first and second plates,

and a source of control pulses selectively coupled to said stacks oftransducers for controlling the lengths of said stacks so that eachstack moves its corresponding area of said first and second plates sothat said first and second plates move to predetermined relativepositions with the corresponding first and second longitudinal sectionof each stack applying equal and opposite reaction forces to saidmounting plate.

9. The combination of claim 8 in which said array has first and secondhalves each corresponding to half of the surfaces of said first andsecond plates and said source of pulses applies a first pulse pattern toa first half of said array and a second pulse pattern inverted withrespect to said first pulse pattern to a second half of said array.

10. The combination of claim 9 in which the transducers are selectivelycoupled to said source of pulses in series and in parallel.

11. A scanner comprising first and second plates having a symmetricalconfiguration with respect to each other and positioned parallel to eachother, at least one of said plates having a reflective surface,

a mounting plate positioned equal distance between and substantiallyparallel to said first and second plates,

a support structure coupled to said mounting plate,

an array positioned between said first and second plates with a firstportion between said first plate and said mounting plate and secondportion between said second plate and said mounting plate, the first andsecond portions of said array formed of a plurality of stacks linearmotion transducer elements being individually controllable to vary inlength between said first and second plates, said arrays beingpositioned so that corresponding stacks of said first and secondportions contact corresponding portions of said mounting plate,

1 1 12 and a source of pulses coupled to the first and second andopposite forces to said mounting plate for canportions of said array forcontrolling the transducer caning Said forces and transferring a minimumof means so that said first and second plates move with a substantiallylinear variation of distances between corresponding points and forapplying equal forces to said support structure.

1. A scanner comprising first and second plates having a symmetricalconfiguration relative to each other and a deflection plane orthogonaland through the surfaces of said plates, mounting means positioned in aplane between and parallel to said first and second plates, an arrayhaving first and second portions and positioned between said first andsecond plates and including a plurality of stacks of linear motiontransducers arranged substantially symmetrical relative to saiddeflection plane, each stack having said first and second portions onopposite sides of said mounting mirror, and a source of pulses coupledto said linear motion transducers so that each stack controls movementof an area of each of said plates so that said first and second plateseach move around a rotation axis included in said deflection plane. 2.An oscillating mirror system comprising first and second circular platesof a rigid material positioned with a selected space therebetween, saidplates divided into first and second semicircular portions on oppositesides of a neutral plane perpendicular to the surfaces of said plates, amounting plate positioned between and parallel to said circular platessubstantially half way therebetween, first and second groups of stacksof transducer elements positioned between said first and second platesat said first and second portions respectively, said stacks positionedin each group in a preselected pattern symmetrical relative to saidneutral plane, each stack having first and second portions positioned onopposite sides of said mounting plate, a source of pulses coupled to thestacks of said first and second groups to apply a first pulse pattern tosaid first group and a pulse pattern inverted with respect to said firstpulse pattern to said second group, whereby said first and second platesare deflected by rotation around an axis through said neutral plane sothat sequentially the first end has a substantially greater spacingbetween said plates than the second end and said second end has asubstantially greater spacing between said plates than the first end. 3.The combination of claim 2 whereby transducer elements energizable bysaid source of pulses and substantially adjacent to first and secondends are connected in parallel and other transducer elements energizableby said pulses are connected with selected combinations of parallel andseries connected transducer elements therebetween.
 4. The combination ofclaim 3 whereby said transducer elements are electrostrictive elementsand the voltage pulse patterns are symmetrical around a referencevoltage with each of said transducers coupled to said reference voltage.5. The combination of claim 3 whereby said transducer elements aremagnetostrictive elements.
 6. A high speed interlace mirror system forreceiving energy from sources on a surface comprising first and secondplates of a symmetrical configuration with respect to each otherpositioned at a predetermined distance apart with at least the surfaceof said first plate being polished to reflect energy received from saidsource, said first and second plates having a neutral plane through thecenter thereof and orthogonal to the surfaces thereof, means formounting said first and second plates positioned in a mounting planebetween and parallel to said first and second plates, a plurality ofdetectors arranged to receive reflected energy from the surface of saidfirst platE, first and second groups of stacks of electrostrictivetransducers positioned in a selected pattern respectively on oppositesides of said neutral plane between said first and second plates, saidstacks having transducers therein selectively connected in parallel andin series with stacks arranged in a predetermined pattern symmetricalaround said neutral plane, each stack having first and second portionsrespectively positioned on opposite sides of said mounting plane, asource of voltage pulses coupled to the stacks of said first and secondarrays, said source of pulses applying a first pulse pattern to saidfirst array and an inverted pulse pattern to said second array, saidfirst pulse pattern and said inverted pulse pattern each having aplurality of voltage levels to define step positions for interlacingenergy from different positions of said surface.
 7. A high speed scanmirror mounted on a support structure comprising first and second platespositioned parallel to each other with the surface of at least oneforming a mirror, said plates having a plane therethrough substantiallyperpendicular to the surfaces thereof, a mounting plate structurepositioned parallel to and between said first and second plates andattached to said support structure, a plurality of electricallycontrolled first and second drive motor means respectively positionedbetween said first plate and a selected position of said mounting platestructure and said second plate and said selected position of saidmounting plate structure adjacent to a selected area of both plates, sothat each corresponding first and second motor means applies equal andopposite reactions to said mounting plate structure to cancel thereactions so that relatively small reactions are applied to said supportstructure.
 8. A controllable structure comprising first and secondplates of a rigid material positioned substantially parallel to eachother, a mounting plate positioned parallel to and between said firstand second plates, an array formed of a plurality of stacks oftransducers positioned between said first and second plates with eachstack having first and second longitudinal sections having controllablelengths, and each contacting a selected position of said mounting plateeach for controlling the distance between said first and second platesand said mounting plate of a selected area of said first and secondplates, and a source of control pulses selectively coupled to saidstacks of transducers for controlling the lengths of said stacks so thateach stack moves its corresponding area of said first and second platesso that said first and second plates move to predetermined relativepositions with the corresponding first and second longitudinal sectionof each stack applying equal and opposite reaction forces to saidmounting plate.
 9. The combination of claim 8 in which said array hasfirst and second halves each corresponding to half of the surfaces ofsaid first and second plates and said source of pulses applies a firstpulse pattern to a first half of said array and a second pulse patterninverted with respect to said first pulse pattern to a second half ofsaid array.
 10. The combination of claim 9 in which the transducers areselectively coupled to said source of pulses in series and in parallel.11. A scanner comprising first and second plates having a symmetricalconfiguration with respect to each other and positioned parallel to eachother, at least one of said plates having a reflective surface, amounting plate positioned equal distance between and substantiallyparallel to said first and second plates, a support structure coupled tosaid mounting plate, an array positioned between said first and secondplates with a first portion between said first plate and said mountingplate and second portion between said second plate and said mountingplate, the first and second portions of said array formed of a pluralityof staCks linear motion transducer elements being individuallycontrollable to vary in length between said first and second plates,said arrays being positioned so that corresponding stacks of said firstand second portions contact corresponding portions of said mountingplate, and a source of pulses coupled to the first and second portionsof said array for controlling the transducer means so that said firstand second plates move with a substantially linear variation ofdistances between corresponding points and for applying equal andopposite forces to said mounting plate for cancelling said forces andtransferring a minimum of forces to said support structure.